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Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ANALYSIS OF FSO SIGNAL TRANSMISSIONUSING DENSE WAVELENGTH
DIVISION MULTIPLEXING METHOD
DISSERTATION-II
Submitted in partial fulfilment of the
Requirement for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
Wireless Communication
By
IFAT RASHEED
Under the Esteemed Guidance of
MR RAJAN MIGLANI
School of Electrical amp Electronics EngineeringLovely Professional University
Punjab
MAY 2017
I
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
PAC FORM
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
CERTIFICATE
This is to certify that the pre-dissertation titled Analysis Of FSO signal transmission
using DWDM method that is being submitted by Ifat Rasheed in partial fulfilment
of the requirements for the award of Master Of Technology Degree(Wireless
Communication) is a record of bonafide work done under my guidance The content of
this report in full or in parts have neither taken from any other source nor have been
submitted to any other Institute or university for award of any degree or diploma and the
same is certified
Mr RAJAN MIGLANI
ASSISTANT PROFESSOR
(LOVELY PROFESSIONAL UNIVERSITY)
Objective of the Thesis is satisfactory unsatisfactory
Examiner I Examiner II
ii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ACKNOWLEDGEMENT
I would like to thank LOVELY PROFESSIONAL UNIVERSITY for giving me
opportunity to use their resource and work in such a challenging environment I am
grateful to the individuals whom contributed their valuable time towards my thesis
I wish to express my sincere and heart full gratitude to my guide MR RAJAN
MIGLANI Assistant professor who guides me to take up this thesis in sync with
global trends in scientific approach
I would also like to extend my gratitude to my friends and family who always
encouraged and supported me in this thesis work
Last but not least I would like to thank all the staff members of department of
Electrical and Electronics engineering who have been very patient and co-operative
with us
IFAT RASHEED
Reg No 11502286
iii
iv
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
DECLARATION
I Ifat Rasheed student of Master of Technology(Wireless Communication)
under Department of ELECTRONICS ENGINEERING of Lovely Professional
University Punjab hereby declare that all the information furnished in this dissertation-
II report is based on my own intensive research and is genuine
This dissertation-II to the best of my knowledge does not contain any part
of my work which has been submitted for the award of my degree without proper
citation
Date
IFAT RASHEED
Registration No 11502286
v
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 2: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/2.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
PAC FORM
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
CERTIFICATE
This is to certify that the pre-dissertation titled Analysis Of FSO signal transmission
using DWDM method that is being submitted by Ifat Rasheed in partial fulfilment
of the requirements for the award of Master Of Technology Degree(Wireless
Communication) is a record of bonafide work done under my guidance The content of
this report in full or in parts have neither taken from any other source nor have been
submitted to any other Institute or university for award of any degree or diploma and the
same is certified
Mr RAJAN MIGLANI
ASSISTANT PROFESSOR
(LOVELY PROFESSIONAL UNIVERSITY)
Objective of the Thesis is satisfactory unsatisfactory
Examiner I Examiner II
ii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ACKNOWLEDGEMENT
I would like to thank LOVELY PROFESSIONAL UNIVERSITY for giving me
opportunity to use their resource and work in such a challenging environment I am
grateful to the individuals whom contributed their valuable time towards my thesis
I wish to express my sincere and heart full gratitude to my guide MR RAJAN
MIGLANI Assistant professor who guides me to take up this thesis in sync with
global trends in scientific approach
I would also like to extend my gratitude to my friends and family who always
encouraged and supported me in this thesis work
Last but not least I would like to thank all the staff members of department of
Electrical and Electronics engineering who have been very patient and co-operative
with us
IFAT RASHEED
Reg No 11502286
iii
iv
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
DECLARATION
I Ifat Rasheed student of Master of Technology(Wireless Communication)
under Department of ELECTRONICS ENGINEERING of Lovely Professional
University Punjab hereby declare that all the information furnished in this dissertation-
II report is based on my own intensive research and is genuine
This dissertation-II to the best of my knowledge does not contain any part
of my work which has been submitted for the award of my degree without proper
citation
Date
IFAT RASHEED
Registration No 11502286
v
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 3: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/3.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
CERTIFICATE
This is to certify that the pre-dissertation titled Analysis Of FSO signal transmission
using DWDM method that is being submitted by Ifat Rasheed in partial fulfilment
of the requirements for the award of Master Of Technology Degree(Wireless
Communication) is a record of bonafide work done under my guidance The content of
this report in full or in parts have neither taken from any other source nor have been
submitted to any other Institute or university for award of any degree or diploma and the
same is certified
Mr RAJAN MIGLANI
ASSISTANT PROFESSOR
(LOVELY PROFESSIONAL UNIVERSITY)
Objective of the Thesis is satisfactory unsatisfactory
Examiner I Examiner II
ii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ACKNOWLEDGEMENT
I would like to thank LOVELY PROFESSIONAL UNIVERSITY for giving me
opportunity to use their resource and work in such a challenging environment I am
grateful to the individuals whom contributed their valuable time towards my thesis
I wish to express my sincere and heart full gratitude to my guide MR RAJAN
MIGLANI Assistant professor who guides me to take up this thesis in sync with
global trends in scientific approach
I would also like to extend my gratitude to my friends and family who always
encouraged and supported me in this thesis work
Last but not least I would like to thank all the staff members of department of
Electrical and Electronics engineering who have been very patient and co-operative
with us
IFAT RASHEED
Reg No 11502286
iii
iv
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
DECLARATION
I Ifat Rasheed student of Master of Technology(Wireless Communication)
under Department of ELECTRONICS ENGINEERING of Lovely Professional
University Punjab hereby declare that all the information furnished in this dissertation-
II report is based on my own intensive research and is genuine
This dissertation-II to the best of my knowledge does not contain any part
of my work which has been submitted for the award of my degree without proper
citation
Date
IFAT RASHEED
Registration No 11502286
v
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 4: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/4.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ACKNOWLEDGEMENT
I would like to thank LOVELY PROFESSIONAL UNIVERSITY for giving me
opportunity to use their resource and work in such a challenging environment I am
grateful to the individuals whom contributed their valuable time towards my thesis
I wish to express my sincere and heart full gratitude to my guide MR RAJAN
MIGLANI Assistant professor who guides me to take up this thesis in sync with
global trends in scientific approach
I would also like to extend my gratitude to my friends and family who always
encouraged and supported me in this thesis work
Last but not least I would like to thank all the staff members of department of
Electrical and Electronics engineering who have been very patient and co-operative
with us
IFAT RASHEED
Reg No 11502286
iii
iv
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
DECLARATION
I Ifat Rasheed student of Master of Technology(Wireless Communication)
under Department of ELECTRONICS ENGINEERING of Lovely Professional
University Punjab hereby declare that all the information furnished in this dissertation-
II report is based on my own intensive research and is genuine
This dissertation-II to the best of my knowledge does not contain any part
of my work which has been submitted for the award of my degree without proper
citation
Date
IFAT RASHEED
Registration No 11502286
v
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 5: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/5.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
DECLARATION
I Ifat Rasheed student of Master of Technology(Wireless Communication)
under Department of ELECTRONICS ENGINEERING of Lovely Professional
University Punjab hereby declare that all the information furnished in this dissertation-
II report is based on my own intensive research and is genuine
This dissertation-II to the best of my knowledge does not contain any part
of my work which has been submitted for the award of my degree without proper
citation
Date
IFAT RASHEED
Registration No 11502286
v
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 6: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/6.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
TABLE OF CONTENTS
TITLE PAGE
PAC FORM ii
CERTIFICATE iii
ACKNOWLEGEMENT iv
DECLARATION v
TABLE OF CONTENTS vi
LIST OF ABBREVATIONS
LIST OF FIGURES
LIST OF TABLES ix
ABSTRACT x
CHAPTER 1 INTRODUCTION 1
11 Introduction to free space optical communication 1
111Working of FSO 2
113 Block diagram of FSO 2
114Advantages of FSO 3
115Applications of FSO 4
12 Multiplexing in optical networks 4
121Need of multiplexing 5
122 Types of multiplexing 5
1221Time Division Multiplexing 6
1222 wavelength Division Multiplexing 6
13 Types of WDM 8
14 Development of DWDM technology 8
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 RATIONALE amp SCOPE OF STUDY
CHAPTER 4 OBJECTIVES OF THE STUDY
CHAPTER 5 RESEARCH METHODOLOGY 17
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 7: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/7.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
51 Dispersion Compensation Techniques 17
511 Design of Uncompensated setup 17
512 Design of Pre-compensated setup 18
513 Design of Post-compensated setup 19
514 Design of Symmetric-Compensated setup 19
52 Amplification Hybrid Amplification 20
521 Design of SOA amplified setup 20
522 Design of EDFA amplified setup 21
523 Design of Hybrid amplified setup 21
CHAPTER 6 RESULTS ampDISCUSSION 22
71 Design of Different Channel DWDM systems 22
712 Using Compensation Techniques 29
713 Using Different Amplifiers 32
72 Simulation Results 35
73 Eye Diagrams 38
74 Simulation Data 40
75 Graphs amp Discussions 49
751 For Different Channel Setups 50
752 For Different Attenuations 50
753 At Different Channel Spacings 51
754 Various Compensation Techniques 52
755 Using various Compensation Techniques 53
76 Varying Amplifiers 58
77 Varying modulation Schemes 59
Conclusion 61
Future Scope 62
Appendix-I 63
References 64
vii
vi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 8: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/8.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF ABBREVATIONS
DWDM Dense Wavelength Division Multiplexing
WDM Wavelength Division Multiplexing
FSO Free Space Optics
LED Light Emitting Diode
BER Bit Error Rate
Q factor Quality factor
PRBSG Pseudo Random Bit Sequence Generator
SNR Signal To Noise Ratio
viii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 9: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/9.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF FIGURES
NAME OF FIGURE PAGE NO
FSO overview 2
Block diagram of FSO 3
Time division multiplexing 6
Wavelength division multiplexing 7
15 Development in DWDM technology 8
511 Uncompensated DWDM system with FSO 18
512 pre-compensated DWDM system with FSO 18
513 post-compensated DWDM system with FSO 19
514 Symmetric-compensated setup 19
521 SOA amplified model 20
522 EDFA amplified model 21
523 Hybrid amplified model 21
611 Different channel setups 22
612 Different compensation setups 29
613 Different Amplifier setups 32
62 Analyser outputs 38
63 Eye diagrams 38
Various channel graphs 50
At various attenuations 50
753 At various channel spacing 51
754 For compensation schemes 53
755 Varying data rates 54
76 Using different amplifiers 59
77 Varying modulation schemes 60
ix
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 10: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/10.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
LIST OF TABLES
NAME OF THE TABLE PAGE NO
1 Data for varying FSO length 40
2 Data for varying FSO attenuation 41
3 Data for varying channel spacing 42
4 Varying FSO length (Uncompensated ) 43
5 Data for amplified setups 44
6 Data for pre- compensated setup 45
7 Data for post-compensated setup 46
8 Data for symmetric compensated setup 47
9 Varying Data rate (uncompensated) 48
10 Varying Modulation format 49
xi
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 11: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/11.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing
ABSTRACT
During the last few years the demand of high speed internet traffic and multimedia services
has been increasing tremendously This increased demand stimulated the use of high
capacity networks which focus on enhancing the transmission capacity and coverage area
Free space optics (FSO) being a medium of high bandwidth with maximum data rates is a
promising technology for providing maximum transmission rate with minimum errors The
transmission rates provided by FSO are very higher than transmission rates possible by RF
technology To support multiple users and make FSO a reliable commercial technique
various channels are multiplexed using Dense Wavelength Division Multiplexing
technique In this paper different DWDM systems varying in terms of number of channels
are designed and the effect of increase in number of channels with respect to increase in
FSO length is observed The DWDM system showing best performance than the other
systems is evaluated for further investigations
The main objective is to vary the system parameters like number of channels attenuation
FSO range type of modulation etc and observe the effect on performance evaluating
parameters such as BER The effect of increase in number of users with respect to increase
in FSO length is investigated The work includes the use of Compensation techniques (Pre-
Post amp symmetric) and hybrid amplifiers like EDFA SOA in FSO based DWDM system
to increase the range of FSO Also the effect of varying channel spacing between the
channels with the variation in FSO length is carried out
It was observed that while analyzing the effect of increase in number of channels 30
channel system performs best followed by 4050 amp 60 channel setupsThe pre post and
symmetric compensation techniques for NRZ link using dispersion compensated fiber(
DCF) for 30 channel setup are analysed and a comparative analysis between systems
employing different compensation techniques is made The simulation results indicate that
the post-compensation scheme having a minimum BER value of 10^-63 at 1 km FSO length
is superior followed by pre compensation symmetric compensation and uncompensated
models with minimum BER values as 10^-5710^-18 amp 10^-29 respectively at 1 km the use
of compensation techniques increased FSO range from 2km to 5km
xii
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 12: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/12.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
1
CHAPTER 1
INTRODUCTION
11 Free Space Optical Communication
In the present era where communication has bought a revolution high speed networks are
highly required which thus focus on increasing the transmission capacity and coverage
area Free space optical communication is one of the most promising technology for
providing transmission rates that are very higher than transmission rates possible by RF
technology[1] Free space optical communication (FSO) has a combined properties of
wireless and optical fiber and is called as optical wireless communication or laser com
(laser communication)FSO is an optical communication technique in which line of sight is
used to meet the demand of high bandwidth over short distances[2]An optical modulated
data is transmitted by FSO using a visible or IR band of frequencies which are unlicensed
part of the spectrum and hence there is no need to pay any charges to the government
agencies This property of FSO system makes it cost efficient technique
Besides the combined properties of fiber optics and wireless in FSO the difference lis in
the transmission medium FSO uses airspace as a transmission medium while fiber optics
uses glass fiber as a transmission medium[1] Therefore the light pulses instead of
transmitting through glass of fiber are transmitted through atmosphere
Free space optical communication is cost efficient flexible simple and have easy
installation Since the transmission medium used in FSO is atmosphere hence digging of
earth for fiber laying is not required this results in both the time and cost efficient nature
of FSO technique
The use of Atmosphere as a transmission medium in FSO limits its performance due to the
atmospheric turbulences that limit this technique to short range distances The atmospheric
turbulences include rain dust fog snow smoke and scintillations These atmospheric
turbulences deteriorate the performance of FSO link To remove these shortcomings some
techniques have been introduced These techniques include
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 13: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/13.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
2
diversity aperture averaging and the use of optical amplifiers for amplification of
signal[2]
Optical amplifiers can be deployed for optical amplification of signals and these optical
amplifiers include Raman SOA or EDFA (Erbium dopped fiber amplifier) EDFA is the
most commonly used optical amplifier and due to its high gain and bandwidth it is used
for multiple wavelength amplification or in other words it can be deployed in WDM
networks easily
The increase in the number of channels and reducing the spacing between the channels
results in the increase in the capacity of the system and hence the increased demand of
broader bandwidth is met This fact led to the introduction of wavelength division
multiplexing (WDM) technique in FSO communication Therefore the increased demand
of broader bandwidth is achieved by using WDM based FSO communication [3]
112 Working
Free space optical communication uses two transrecievers at both the ends for providing
full duplex communication The network traffic is first converted into the pulses of
invisible light representing binary 1rsquos and 0rsquos Infra red waves are generated by LED and
Laser diodes at a transmitter side that act as a carrier for data transmission
Fig 11FSO Overview
113 Block diagram of FSO
The block diagram of FSO is shown in figure 12
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 14: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/14.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
3
Fig 12 Block diagram of a terrestrial FSO system [3]
The components of block diagram of FSO communication system are explained as
follows
(i) Transmitter
The transmitter is primarily concerned with the modulation of the source data The
modulation is done by using optical signal as a carrier and intensity modulation is the
most common type of modulation used Intensity modulation refers to the modulation of
source data where irradiance of optical signal is used as a carrier wave This modulation
can be performed either directly by an external modulator (like symmetric Mechzender
interferometer) or by directly changing driving current of optical source in response to
the transmitter information[3]
(ii) Atmospheric channel
An atmospheric channel is composed of gases aerosols and suspended tiny particles
Some atmospheric turbulence includes rain dust fog snow and scintillations
(iii) Receiver Receiver retrieves the source data from incident optical field The
components of receiver are receiver telescope optical band pass filter and photo
detector and decision circuit post demodulation process
114 Advantages of FSO
(i) FSO technique does not require any RF license from any of the agencies as the signal
is optically modulated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 15: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/15.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
4
(ii) There is no interference of the signal by the radio frequencies hence fewer
disruption to the information flow
(iii) Digging of streets and no expensive rooftop installation is needed
(iv) No security upgrades are required as there is a line of sight based communication
(v) The data rates provided by FSO channels is very high as compared to that of the RF
links and it operates on the frequency range of up to 3THZ
115 Applications of FSO
FSO links are used in a number of fields Some of the applications are described below
(i) Outdoor wireless access FSO do not require any license from any agency hence it
can be used for communication by wireless service providers
(ii) Last mile access To dig the streets for fiber laying in the last mile is very costly
FSO can be implemented in the last mile along with other networks
(iii) Enterprise connectivity FSO being an easily installing technique is used for
interconnecting LAN segments to enable communication between two buildings etc
(iv) Fiber backup In case of a failure transmission through a fiber link FSO can be
used in providing a backup link
(V ) Military access FSO being a secure and undetectable technique can connect large
areas safely with minimum planning
12 Multiplexing In Optical Networks
Multiplexing is a technique of combining multiple message signals into a single
composite signal for transmission over a shared medium To transmit several signals
over the same medium and separate these signals easily at the receiver end the signals
must be kept apart so as to avoid the interference between the signals
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 16: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/16.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
5
Due to the higher bandwidth of optical fibres the high speed data and video applications
prefer to get transmitted through such a medium There are several types of multiplexing
and the two most commonly used are Wavelength division multiplexing and Time
division multiplexing
Since digital signal transmission is best supported by optical fibre electronic parallel to
serial converters like Agilent G-link or cypress Hotlink are used for the time division
multiplexing of many low rate digital information Many low speed data signals are
merged into a composite high rate channel for transmission and is then regenerated at the
receiver end
Wavelength division multiplexing is a technique of transmitting multiple wavelengths on
a single optical fibre Multiple wavelengths of light like different colours propagate
through a single optical fibre without interfering each other [5] Such Devices that
perform the optical combining at the transmitter side and the optical separation at the
receiver side are called as WDMs
121 Need Of Multiplexing
Since the bandwidth of communication media is very large and it has been observed that
most of the devices involved in the communication of individual data signals utilize
medium data rate As a result whole capacity of data link is not utilised Hence when
the bandwidth of communication media is much higher than the single data signals that
are to be transmitted via medium medium can be shared by the multiple transmitting
signals so as to make effective utilisation of available channel capacity Multiplexing
also results in cost reduction simplification of driver electronics and direct interface with
the microprocessors [6]
122 Types Of Multiplexing
The property of higher bandwidth of optical fibre makes it a preferred medium for the
propagation of high speed data and video applications Different types of multiplexing
are needed to make use of this bandwidth [6] The most common forms of multiplexing
are Wavelength division multiplexing and Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 17: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/17.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
6
1221 Time Division Multiple Access
Time division multiplexing is a type of multiplexing in which the data is transmitted
and received over a common individual channel by the use of synchronised switches on
both the ends of transmission medium as a result of which the transmitted signals appear
on a medium in an alternating manner only a fraction of time Time division
multiplexing is mainly used for digital signals but analog signals can also be
multiplexed by using time division multiplexing in a way that multiple data signals are
transmitted such that they appear as subndashchannels simultaneously in a single
communication channel but physically take turns on the channel The Time domain is
divided into various repeated time slots having fixed length and one time slot per sub-
channel During time slot 1 a data signal of sub-channel 1 is transmitted during time
slot 2 a data signal of sub-channel 3 is transmitted etc One time slot per sub-channel a
synchronisation channel and sometimes error correction channel before the
synchronisation constitute one TDM frame channel
Time division multiplexing is a technique of accessing a channel for shared medium
networks Different users are allowed to share a common frequency channel by dividing
the signal into several time slots [7] The users transmit the data successively each
utilising its assigned time slot This results in the sharing of common communication
medium by the multiple users making use of only the part of medium capacity
Fig 13 Time division multiplexing [8]
1222 Wavelength Division Multiplexing
In order to meet the increasing demand of large amounts of bandwidth the capacity of
optical fibres was found to be insufficient by the services like high internet traffic (video
conferencing and streaming audio) and multimedia services Time division multiplexing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 18: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/18.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
7
has been used to increase the capacity but due to some of its drawbacks like allowing
multiplexing only up to 10 Gbs lead to the introduction of wavelength division
multiplexing in the field of telecommunication Wavelength Division Multiplexing is
one of the most promising technology that can utilise the available bandwidth of the
fibre
Wavelength Division Multiplexing is associated with the division of optical transmission
spectrum into several number of non-overlapping wavelength bands such that each
wavelength supports an individual communication channel operating at highest
electronic speed[9] Therefore the huge bandwidth can be utilised by the different
wavelengths that exist simultaneously on a single optical fibre
Wavelength Division Multiplexing is a method of multiplexing various optical carrier
signals having different operating wavelengths (like different colours of laser light)This
technique results in bidirectional communication over a single optical fibre and also
result in the multiplication of capacity
A wavelength division multiplexing system consists of a multiplexer at the transmitter
side that combines the multiple signals from the multiple users and a demultiplexer at the
receiver side that seperates the signals at the receiver end
Most of the WDM systems are used in single mode fibres having a core diameter of
9microm However some forms operate in multimode fibres having a core diameter of 50microm
or 625microm[10]
Fig 14 Wavelength Division Multiplexing [11]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 19: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/19.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
8
13 Types Of WDM
Depending on the channel spacing WDM systems are classified in the following classes
(a) Simple WDM This kind of WDM is made by using very simple and less costly
components and this principle is being used by a number of applications from a number
of years
(b) Dense WDM This type of WDM has channel spacing less than 1 nm Hence it
refers to the close spacing of channels
(c) Coarse WDM This type of WDM has channel spacing of more than 5nm hence the
number of channels is lesser than in dense wavelength division multiplexing (DWDM)
and greater than in standard wavelength division multiplexing (WDM)
14 Development Of DWDM Technology
The concept of Wave Division Multiplexing in optical fiber communication was
introduced in the late 1980rsquos where two broadly spaced wavelengths in the regions of
1310 nm amp 1550 nm ( or 850 nm amp 1310 nm) were used this is sometimes known as
wide band WDM[3] The second generation of WDM called as Narrow Band WDM was
introduced in early 1990rsquoswhich supported two to eight channels having a channel
spacing of about 400 GHZ in the 1550 nm window After that Dense Wavelength
Division Multiplexing (DWDM) evolved in the mid-1990rsquos supporting 16 to 40
channels having channel spacing from 100 to 200 GHZ However in the late 1990rsquos the
advancements in DWDM led to the support of 64 to 160 parallel channels having dense
packing at 50 or even 25 GHZ intervals[12]
Fig 15 Development in DWDM technology[12]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 20: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/20.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
9
CHAPTER 2
LITERATURE REVIEW
For completion of my thesis following research articles were referred and followed
primarily
1) SOORAJ PARKASH ANURAG SHARMA HARSUKHPREET SINGH amp
HARJIT PAL SINGH(2016) This research article is about the demonstration of a
DWDM based FSO communication system working on 8 channels with channel spacing
of 08 nm and each channel having a data rate of 5 GBs such that the overall data rate of
a system is 40 GBs The range of FSO link is 4km The study also concludes that bit
error rate increases sharply when the range of FSO is increased beyond 4km[2]
2)SIMRANJIT SINGH amp RSKALER(2014) This paper presents the design of novel
flat-gain amplifier using a hybrid combination of Er-Yb co-doped amplifier (EYDWA)
and a semiconductor optical amplifier (SOA) for 10010-Gbs dense wavelength
division multiplexed system at 02 nm interval as a result of which a flat gain of gt14 dB
is obtained across the effective bandwidth with a gain variation of 075 db without using
any gain clamping techniques This proposed hybrid amplifier reduce the gain of DRA-
EDFA HOA from approximately 201 to 115 dB efficiently Hence resulted in
improved performance in terms of cost gain flatness etc [13]
3)XIAOJIE GUO amp CHESTER SHU(2014) In this paper backward Raman pump
has been used to reduce the cross gain modulation for multi wavelength amplification in
a fiber optical amplifier (FOPA) and a comparison is made between the performances of
two wavelength amplifications of FOPArsquos with and without Raman pump under the
condition of identical unsaturated gains This resulted in the reduction of cross gain
modulation of one channel due to the presence of other WDM channel having high input
power as compared to the conventional FOPA having identical unsaturated gain Hencea
power penalty of 63 dB is obtained for a 10-Gbs RZ-OOK signal at a BER of 10-8 [14]
4)MAHMOUD JAZAYERIFAR STEFAN WARMROBERT ELSCHNER
DIMITAR KROUSHKOV et al (2013) The authors have derived the analytical
expressions for the performance of long-haul DWDM communication system employing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 21: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/21.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
10
in-line phase sensitive fiber optic parametric amplifiers(FOPA)The errors due to
transmission fibers and FOPArsquos are considered and the model is then verified using
simulations The performance of FOPA is compared with EDFA and it is observed that
the broad band long haul DWDM transmission system based on FOPArsquos could be
feasible[15]
5) HARDEEP SINGH amp SUKHWINDER SINGH (2014) This paper investigates the
performance of hybrid amplifiers- RAMAN-EDFA RAMAN-SOAEDFA-SOA in
WDM systems having 120 channels with each channel having data rate of 10 Gbs and
reduced channel spacing of 50 GHZ The performance has been compared by varying the
different parameters like fiber length Q factor BER etc and it is observed that RAMAN-
EDFA is the best alternative to RAMAN-SOA amp EDFA-SOA in high capacity WDM
system with reduced channel spacing[16]
6) XIAOJIE GUO amp CHESTER SHU(2015) The authors investigated both
theoretically and experimentally the reduction of four wave mixing crosstalk in multi-
wavelength amplification in backward pumped Raman assisted fiber optical parametric
amplifier (FOPA)A suppression of more than 7 dB in FWM crosstalk initiated from
both degenerate ndashFWM and non degenerate ndashFWM has been obtained The authors also
described the effects of signal channel number and the powers of the parametric pump
and the Raman pump on the FWM crosstalk[17]
7) SIMRANJIT amp RSKALER (2013) This paper provides the demonstration of an
efficient gain-flattened L-band optical amplifier using a hybrid configuration of
distributed Raman amplifier(DRA) and an erbium-doped fiber amplifier (EDFA) for
16010 Gbs dense wavelength division multiplexed system at 25-GHZ interval A flat
gain of gt10dB is obtained with an input signal power of 3 mW across the frequency
range from 187 to 190975 THZ having a gain variation of lt45 dB without the use of
any gain flattening technique [18]
8) THOMAS TOROUNIDIS(2003)This paper demonstrates experimentally the
performance of fiber optical parametric amplifier(FOPA) in WDM applications for the
first time The authors investigate both 3 10 GBs and a commercial 725 Gbs WDM
system with the parametric amplifier This paper also presents the performance in terms
of power penalty and gain versus input-output signal power [19]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 22: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/22.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
11
9) MFC STEPHENS(2015)The authors of this paper demonstrate experimentally a
Raman Assisted Fiber Optical Parametric Amplifier(RA-FOPA) having 20 dB net gain
using WDM signals They also reported amplification of 1058 Gbs 100 GHZ-spaced
QPSK signals and showed that the gain improvement of upto 5 dB can be obtained for
the RA-FOPA by properly tuning parametric pump and compared with the combined
individual contribution from the parametric and Raman pumps Also RA-FOPA is
compared with a conventional FOPA having same gain and it was observed that the four
wave mixing crosstalk is suppressed upto 58plusmn04 dB using RA-FOPA[20]
10) ECIARAMELLAYARIMOTOGCONTESTABILEMPRESIAD
ERRICOVGUARINO amp MMATSUMOTO (2009) This paper provides the highest
transmission rate of 3240 Gbps that is four times greater than the results obtained in the
previous studies The system is also upgraded to its highest capacity of 128 Terabits
which was the highest capacity obtained than the capacity obtained in the previous
results[21]
11) VISHAL SHARMAGURIMANDEEP KAUR (2013) The authors of this paper
analysed the architecture of multipath fading resistant fading communication system using
OFDM multicarrier scheme along with OTSB (optical tandem side band) and OSSB
(optical single side band) schemes This system provided a great flexibility in the
atmospheric turbulences like fog haze etc that affect the performance of FSO
communication system and hence resulted in increase in the transmission rate The study
also reveals that due to the large immunity against fading the performance of OSSB is
better than OTSB at high data rates[22]
12) SOORAJPARKASH ANURAG SHARMAMANOJ KUMAR amp
HARSUKHPREET SINGH(2015) In this paper a WDM-PON(wavelength division
multiplexing- passive optical network) based FTTH ( fiber to the home) is designed
aiming to offer the high data rates (GBS) to the residential subscribers and the data rate
transmission was upgraded to 2032 GBS(640 GBS)Also The appreciable values of bit
error rate are obtained[23]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 23: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/23.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
12
13) GNYKOLAKPFSZAJOWSKIACASHIONHMPRESBY GETOURAGEE
amp JJAUBORN The authors of this paper obtained the data rate of 40Gbs over a free
space optical link of 44 km in a DWDM based FSO communication system The designed
system works on 16 separate channels having 200Ghz of channel spacing between
them[24]
14) JASVIR SINGHPUSHPA GILAWAT ampBALKRISHNA SHAH(2014) In this
paper a WDM based FSO communication system is developed The system supports 32
channels each having a data rate of 40 Gbps over a range of 1km of FSO link using NRZ
and RZ line coding The results also showed that NRZ performs better than RZ line coding
technique[25]
15) AMNINDER KAURSUKHBIR SINGH amp RAJEEV THAKUR(2014) This paper
includes review of free space optics In this paper the authors have discussed FSO and its
need improvements that can be made in FSO technique and the use of FSO technology in
DWDM systems The various parameters that limit the performance of FSO system like
atmospheric turbulences including scintillation losses fog attenuation etc have also been
discussed[26]
16) POOJA KUMARI amp RAJEEV THAKUR(2013) The authors in this paper
proposed the use of hybrid amplifiers in FSO system FSO technique has been discussed
in detail Different types of hybrid amplifiers their features and comparison are discussed
It has been observed that the Raman ndashEDFA[27]
17) SGUIZANI A CHERITI M RAZZAK Y BOUSLIMANI amp
HHAMAM(2005) The authors in this paper incorporated a post-compensation
technique to optically compensate the chromatic dispersion in fiber A temporal effect is
used by a fiber having a range beyond 40Gbits[28]
18) RAJANI RAJU PAL amp VISHAL SHARMA (2012) In this paper various
compensation techniques including pre-compensation post- compensation and symmetric
compensation are used by using standard mode fiber and dispersion compensated fiber
and a comparative analysis between these compensation techniques is made at data rate of
1015 Gbps at different modulation formats and different optical power levels It was
observed that post and symmetric compensated systems showed better results[29]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 24: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/24.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
13
19) MOHAMMAD ALI KHALIGHIMURAT UYSAL(2014) In this paper a detailed
theoretical information about FSO channel models and transmitterreceiver structure have
been discussed by the authors The limitations of FSO system and algorithmic level
system designs have been discussed to overcome these limitations[30]
20) ALLA ABBAS KHADIR BAYDAA FDHAHIR amp XIQUAN FU(2014) In this
paper the simulation of various systems using different techniques by optisystem program
is discussed The main aim of authors is to make the use of optisystem clear to the ones
who are not aware of it Various simulation models like DWDM system DCF system
DBM system have been designed and simulated by the author using optisystem
program[31]
21) ANKITA SHIVHARE ANKITA MOWAR ampSONI CHIGLANI(2015)In this
paper the authors demonstrated the behaviour of optical wireless communication system
by varying the aperture of FSO link The simulation results indicate that the variations in
FSO aperture result in improving distance of FSO[32]
22) VISHAL SHARMAMINI LUMBA amp GURMANDEEP KAUR(2014)In this
paper authors have demonstrated CDMA-FSO coherent detection system with 10 Gbps
data rate and reasonable SNR under the effect of atmospheric turbulences like rain snow
etc[33]
(23) SHAO HAO WANG LIXIN XUPKAWAI amp HWA YAW TAM(2011) In this
paper the authors investigated the gain of Raman assisted fiber optical amplifier Also a
normalised phase-matched model is proposed to achieve the performance of peak value of
gain of RA-FOPAs that operate in low magnitude region [34]
(24) RSKALERAJAY K SHARMA amp TSKAMAL(2002) The authors in this paper
have demonstrated the compensation schemes (pre-post-symmetric) in a system with
10Gbps data rate ampNRZ modulation by using single mode fiber amp dispersion compensated
fiber to achieve transmission at high data rates It is observed that symmetric
compensation is superior followed by post-amp pre compensation schemes [35]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 25: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/25.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
14
(25)MANPREET KAURHIMALI SARANGAL(2015)In this paper compensation
techniques are used to investigate 40 Gbps WDM system by using dispersion compensated
fiber Also comparative analysis is made at the receiving side with respect to variation in
different parameters[36]
(26) MANPREET KAURHIMALI SARANGAL(2015) In this paper authors have
compensated the dispersion of a fiber by using dispersion compensated fiber at 20 Gbps
Three compensation schemes(pre- post- amp symmetric-) have been used and a
comparative analysis between these schemes is made[37]
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
![Page 26: ANALYSIS OF FSO SIGNAL TRANSMISSION USING DENSE …](https://reader031.vdocument.in/reader031/viewer/2022011913/61d7739be337837e163fd9d4/html5/thumbnails/26.jpg)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
15
CHAPTER 3
RATIONALE amp SCOPE OF THE STUDY
31 Rationale
bull FSO communication is the promising technology for providing maximum data rates
with minimum errors
bull In the past years the use of optical fibers proved to be a very costly technique FSO
on the other hand do not require any spectrum fees henceforth a cost efficient
technique
bull DWDM allows multiplexing of signals that can provide data rates upto 100 Gbps
Therefore transmission at maximum data rates is possible
bull DWDM leads to interference and losses due to many reasons like less channel
spacing etc
bull Compensation schemes are proposed to combat the losses that occur due to minimum
channel spacing or that are incurred in the atmospheric channel Pre- Post and
symmetric compensation schemes are used to deliver the data at reasonable BER
values
32 SCOPE OF THE STUDY
bull Free space optical links are highly affected by atmospheric degrading effects like rain
snow fog turbulence etc which reduces the effective line of sight link length
bull DWDM allows multiple users to provide a high data rate communication and if the
same is used with FSO then optical signal can reach the end user
bull Tuning of hybrid optical amplifiers to support FSO signal
bull To design FSO-DWDM system which can deliver reasonable performance over long
distances
bull To design FSO-DWDM system to operate with higher number of multiplexed users to
ensure higher bandwidth and capacity utilization
bull To investigate the performance of FSO-DWDM link for reduced channel spacing
bull To investigate the effect of pre-post- and symmetric compensation techniques in
improving the link reliability
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
16
CHAPTER 4
OBJECTIVES OF THE STUDY
bull To investigate the performance of FSO link using DWDM technique
bull To evaluate and design suitable FSO-DWDM link using compensation techniques to
enhance link reliability
bull To evaluate performance of FSO-DWDM link for reduced channel spacing using
different optical modulation techniques
bull To optimise FSO-DWDM link so that desired link characteristics can be maintained
for data rates higher than 10Gbps
bull To design FSO-DWDM link that can support multiple users in excess of 30 in
number for decreased values of channel spacing
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
17
CHAPTER 5
RESEARCH METHODOLOGY
This chapter describes the methodology and the approaches that were followed to complete
this research work The whole research work revolves round the simulation software-
Optisystem(version 70)The primary aspect of the methodology includes the process of
simulation The main aim of simulation is to design different DWDM systems with FSO
transmission link varying in number of channels and to apply the use of hybrid amplifiers
and compensation techniques for increasing the transmission distance The number of
channels are varied as 30 40 50 and 60 and the transmission distance is varied from 1 km
to 5 km The system with 30 channels showed better performance followed by 40 50 and 60
channel systems and this 30 channel system is considered for further study The
compensation techniques used are pre-compensation post-compensation and symmetric
compensation A Hybrid combination of EDFA and SOA amplifiers are also used in a
DWDM system and the performance of system is evaluated The study also includes the
variation of various parameters including attenuation channel spacing data rates
modulation format with respect to the change in FSO length and observing the effect on
performance of the system
The dissertation was completed in the following stages
51 Dispersion Compensation Techniques
511 Design of different FSO based DWDM systems varying in number of channels
without use of any compensation technique-Uncompensated simulation model
A simple 30 channel DWDM system was designed by simulating a DWDM transmitter with
DWDM receiver using FSO channel as a transmission medium The system was redesigned
and upgraded for 40 50 and 60 channels also The simulation was done using optisystem
(version 7) The performance of these systems is evaluated with respect to change in FSO
length and It was observed that the 30 channel system showed better performance followed
by 40 50 and 60 channel systems Henceforth 30 channel system is considered for further
study
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
18
Fig 511 Uncompensated DWDM system with FSO channel
512 Design of a 30 channel FSO based DWDM system incorporating Pre-
compensation technique
A 30 channel DWDM system was designed in which FSO link was introduced as a
communication medium and a dispersion compensated fiber (DCF) was deployed before
FSO link to remove the losses that occur due to dispersion A negative dispersion optical
fiber is termed as Dispersion Compensated Fiber The design of a Dispersion Compensated
Fiber involves upgrading a standard mode fiber (SMF) by taking its dispersion value as
negative so that an ordinary fiber can get its positive dispersion value compensated
Fig 512 Pre- compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
TX 1
TX n
TX 2
MUX Atmospheric
channel
DEMUX
RX 1
RX 2
RX n
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
19
513 Design of a 30 Channel FSO Based DWDM system incorporating a Post-
compensation technique
A 30 channel DWDM system was designed by incorporating a dispersion compensated
fiber after the FSO channel The role of using dispersion compensated fiber is to
compensate the positive value of dispersion of an ordinary fiber by setting its dispersion as
a negative value The FSO length is varied from 1 km to 5 km and the effect on the
performance of the system is evaluated in terms of performance evaluating parameter called
as Bit Error Rate (BER)Post- compensation technique when employed in FSO based
DWDM system showed better performance than the other compensation techniques
Fig 513 Post- compensated DWDM system with FSO channel where OA is Optical amplifier amp DCF is
dispersion compensated fiber
514 Design of a 30 Channel FSO Based DWDM system incorporating a Symmetric-
compensation technique
A 30 channel DWDM system is designed in which FSO link is taken as a transmission
medium and pre-post compensation technique ( symmetric compensation ) is applied in the
system A dispersion compensated fiber is incorporated before the FSO channel and after
the FSO channel to compensate the positive dispersion values and the performance of the
system is evaluated in terms of BER values
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
20
Fig 514 Symmetric - compensated DWDM system with FSO channel where OA is Optical amplifier amp
DCF is dispersion compensated fiber
52 Amplification Hybrid Amplification
521 Design of a 30 channel FSO Based DWDM system using Semiconductor Optical
amplifier (SOA)
A 30 channel DWDM system using FSO link as a transmission medium and semiconductor
optical amplifier for compensating the losses incurred in the communication channel is
designed Therefore 30 data streams when combined in a composite signal and send
through FSO channel is amplified by using SOA which ensures that the SNR levels are
boosted to compensate the losses
Fig 521 DWDM system with FSO channel amp SOA where SOA is Semiconductor Optical amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
21
522 Design of a 30 channel FSO Based DWDM system using Erbium Dopped Fiber
Amplifier (EDFA)
A 30 channel DWDM system is designed in which atmospheric channel acts as a
transmission medium and Erbium dopped fiber amplifier (EDFA) is incorporated for
amplifying the signal obtained after multiplexing various data streams and passed through
FSO channel The role of EDFA is to amplify the signal and compensate the losses incurred
by FSO channel The performance of the system is evaluated in terms of BER value
Fig 522 DWDM system with FSO channel amp EDFA where EDFA is Erbium Dopped Fiber
amplifier
523 Design of a 30 channel FSO Based DWDM system using hybrid combination of
Erbium Dopped Fiber Amplifier amp Semiconductor Optical Amplifier (SOA)
A 30 channel DWDM system with FSO link and a hybrid combination of EDFA and SOA
amplifiers was designed The role of using hybrid amplifiers is to amplify the signal and
censure that the SNR value is boosted to compensate the losses incurred in FSO channel
The performance of the system is evaluated and a comparative analysis between the systems
using SOA EDFA and hybrid combination respectively is made graphically
Fig 523 DWDM system with FSO channel amp Hybrid amplifier EDFA+SOA where EDFA is Erbium
Dopped Fiber amplifier amp SOA is Semiconductor optical Amplifier
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
22
CHAPTER 6
Results and Discussions
61 Simulation Setups
Various setups were designed and validated using optisystem 7The proposed designs and
their results are listed in the following sections
611 Design of Different FSO based DWDM systems varying in number of channels
(1) FSO trans-receiver for 30 channels
Fig611(1) (a) transmitter section
Fig 611(1) (b) Transmitter Sub-System
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
23
Fig 611 (1) (c) Receiver section
Fig 611(1) (d) Receiver Sub-System
In above figures an FSO system was designed for 30 data channels The individual data
channels were simulated at different CW LASER frequencies with a mutual frequency
spacing of 08nmThe data channels after going through electrical and optical modulation
techniques are multiplexed using 30X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X30 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
(2) FSO trans-receiver for 40 channels
The same simulation model of 30 channels was redesigned and upgraded for 40 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
24
different CW LASER frequencies with a mutual frequency spacing of 08nmThe data
channels after going through electrical and optical modulation techniques are multiplexed
using 40X1 WDM MUX and then the composite optical signal is transmitted through FSO
channel The systems are optimized in layout using transmitter subsystems and receiver
subsystems as shown in figures 711(1) (b) amp (d) The intercepted signal at receiver is de-
multiplexed using 1X40 WDM De-MUX and then detected back using PIN photo-detectors
and electrical filters to retrieve back the original baseband The system performance is
evaluated using spectral analyzers and BER analyzers
Fig611(2) (a) transmitter section front end part
Fig611(2) (b) transmitter section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
25
Fig611(2) (c) Receiver section front end part
Fig611(2) (d) Receiver section back end part
(3) FSO trans-receiver for 50 channels
The same simulation model of 30 channels was redesigned and upgraded for 50 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 50X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X50 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
26
original baseband The system performance is evaluated using spectral analyzers and BER
analyzers
Fig611(3) (a) transmitter section front end part
Fig611(3) (b) Transmitter section back end part
Fig611(3) (c) Receiver section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
27
Fig611(3) (d) Receiver section back end part
(4) FSO trans-receiver for 60 channels
The same simulation model of 30 channels was redesigned and upgraded for 60 channels
An FSO system was designed for 40 data channels The individual data channels were
simulated at different CW LASER frequencies with a mutual frequency spacing of
08nmThe data channels after going through electrical and optical modulation techniques
are multiplexed using 60X1 WDM MUX and then the composite optical signal is
transmitted through FSO channel The systems are optimized in layout using transmitter
subsystems and receiver subsystems as shown in figures (b) amp (d) The intercepted signal at
receiver is de-multiplexed using 1X60 WDM De-MUX and then detected back using PIN
photo-detectors and electrical filters to retrieve back the original baseband The system
performance is evaluated using spectral analyzers and BER analyzers
Fig611(4) (a) transmitter section front end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
28
Fig611(4) (b) transmitter section back end part
Fig611(4) (c) Receiver section front end part
Fig611(4) (d) Receiver section back end part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
29
612 Design of 30 channel FSO based DWDM systems using different compensation
techniques
(1) Pre-Compensated Simulation Model
Fig 612(1) (a) amp(b) show the setup for 30 channel FSO system incorporating Pre-
compensation technique Here the 30 data streams after forming the composite optical signal
is pre-compensated before its transmission through FSO channel This ensures the SNR
levels are pre-boosted to compensate the losses that are likely to be incurred in FSO
channel The transmitter subsystem and receiver subsystem are shown in fig 711(1)(a)
amp(b)The pre-compensation is carried by using a dispersion compensated fiber and optical
amplifier just before the FSO channel The dispersion compensated fiber is obtained by
taking the dispersion value of an ordinary fiber as negative such that the positive dispersion
s compensated The system showed considerable improvements in performance evaluating
parameters such as BER Q-Factor Eye Height and threshold values compared to
uncompensated setups The performance of pre-compensated setup is also better than
symmetric compensated model
Fig612 (1) (a) Pre-compensated Transmitter part
Fig612 (1) (b) Pre-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
30
(2) Post-Compensated Simulation Model
In the setup shown in Fig612(2)(a) amp(b) an FSO system for 30 data channels was
designed which incorporates a dispersion compensation mechanism using dispersion
compensated fiber and optical amplifier placed after FSO transmission link The transmitter
subsystem and receiver subsystem are shown in fig 711(1)(a) amp(b) In this setup the losses
incurred by transmission through FSO channel are compensated by dispersion compensated
fiber (DCF)and the use of optical amplifier ensures the boosting of signal obtained after
compensating losses by dispersion compensated fiber The system performance showed
considerable improvements in the performance evaluating parameters in comparison to the
other compensation schemes When compared to the other compensation schemes and the
uncompensated model post-compensation is superior and showed the better results than
others The comparison is made graphically where it becomes clear that the BER values
obtained in the post compensation scheme are lower than the other relative techniques
Henceforth the performance is better
Fig612 (2) (a) Post-compensated Transmitter part
Fig612 (2) (b) Post-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
31
(3) Symmetric-Compensated Simulation Model
In Fig 612(2) an FSO based DWDM system is designed using a symmetric compensation
scheme This simulation model merges the pre-compensation and post-compensation
techniques in a single model termed as symmetric compensated model and the scheme is
called as symmetric compensation scheme A combination of dispersion compensated fiber
and optical amplifier are incorporated before and after the FSO channel to compensate the
looses and boost SNR values When compared with other compensation schemes
Symmetric compensation scheme shows almost a linear performance However the
performance is better than the uncompensated simulation model
Fig 612 (3) (a) Symmetric-compensated Transmitter part
Fig 612 (3) (b) Symmetric-compensated Receiver part
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
32
613 Design of 30 channel FSO based DWDM systems using different Amplifiers
(1) Using Erbium Dopped Fiber Amplifier (EDFA)
Figure 6113(1) shows a design of a DWDM system using FSO channel as a transmission
medium 30 data streams are multiplexed in a composite signal which is passed through the
transmission medium An Erbium Dopped Fiber Amplifier (EDFA) is incorporated after the
FSO channel to amplify the signal so as to reduce the losses The performance of the
system is evaluated in terms of BER value and is analysed graphically
Fig613 (1) (a) Transmitter part of FSO based DWDM system using EDFA
Fig613 (1) (b) Receiver part of FSO based DWDM system using EDFA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
33
(2) Using Semiconductor Optical Amplifier (SOA)
An FSO based DWDM system is designed and simulated and semiconductor optical
amplifier (SOA) is incorporated in the setup after the atmospheric channel 30 signals
varying in their wavelengths are combined in a single composite signal and passed through
an atmospheric channel Since the multiplexed signal comes across a number of losses in an
atmospheric channel therefore an Erbium Dopped Fiber Amplifier is incorporated after
FSO channel to reduce these losses The system showed considerable improvements in
performance evaluating parameters such as BER Q-Factor Eye Height and threshold values
compared to unamplified setups
Fig613 (2) (a) Transmitter part of FSO based DWDM system using SOA
Fig613 (2) (b) Receiver part of FSO based DWDM system using SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
34
(3) Using Hybrid combination of Erbium Dopped Fiber Amplifier (EDFA)
Semiconductor Optical Amplifier (SOA)
In figure 713(3) an FSO system for 30 data channels was designed which incorporates an
amplification mechanism using hybrid combination of optical amplifiers placed after FSO
transmission link In this setup the losses incurred by transmission through FSO channel are
compensated by Hybrid amplification setup including semiconductor optical amplifier and
an EDFA The system performance showed considerable improvements in the performance
evaluating parameters in comparison to the ones using SOA or EDFA
Fig613 (3) (a) Transmitter part of FSO based DWDM system using EDFA and SOA
Fig713 (3) (b) Receiver part of FSO based DWDM system using EDFA amp SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
35
62 Simulation Results
The designed setups were simulated and evaluated multiple times for various performance
evaluating parameters The extracted results are listed in the form of Analyzer outputs
Time Domain analyzers BER analyzers and power meters The outputs extracted from
various proposed setups are listed here
a) Analyzer Outputs
Fig 72 (a) Tx1 for 30 Channel FSO Fig 72 (b) Rx1 for 30 channel FSO
(c) Tx1 for 40 Channel F SO (d) Rx1 for 40 Channel FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
36
(e) Tx1 for 50 Channel FSO (f) Rx1 for 50 Channel FSO
(g) Tx1 for 60 Channel FSO (h) Rx1 for 60 Channel FSO
(i) Tx1 for 30Channel pre-compensated FSO (j) Rx1 for 30Channel pre-compensated FSO
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
37
(k) Tx1 for 30Channel post-compensated FSO (l) Rx1 for 30Channel post-compensated
FSO
(m) Tx1 for 30Channel sym-compensated FSO (n) Rx1 for 30Channel sym-compensated
FSO
(o) Tx1 for 30Channel FSO using SOA (p) Rx1 for 30Channel FSO using
SOA
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
38
(q) Tx1 for 30Channel FSO using EDFA (r) Rx1 for 30Channel FSO using EDFA
(s) Tx1 for 30Channel FSO with SOA amp EDFA (t) Rx1 for 30Channel FSO with SOA amp
EDFA
73 Eye Diagrams
Eye diagrams at the reception are a means of depicting how well the transmission has been
in terms of error rates and quality factors Various eye diagrams obtained are shown in
below figures
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
39
Fig73 (a) 30 channel DWDM with FSO (b) 40 channel DWDM with FSO
(c) Rx 1 of 50 channel DWDM with FSO (d) Rx 1 of 60 channel DWDM with FSO
(c) Rx 1 of 30 channel pre-compensated setup (d) Rx 1 of 30 channel post-compensated setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
40
(e) Rx 1 of 30 channel sym-compensated setup (e) Rx 1 of 30 channel setup using SOA
(g) Rx 1 of 30 channel setup using EDFA (h) Rx 1 of 30 channel setup using EDFA amp
SOA
74 Simulation Data
The data extracted from various analyzers is tabulated as follows
Table1 Data for uncompensated Setups (varying FSO Length)
Data MinBER Log(MinBER)
Rate(Gbps)
30 Channel setup
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
41
Table2 Data for uncompensated Setups (Varying FSO Attenuation)
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
40 channel setup
1 762E-15 -141177761
2 745E-09 -8127721326
3 1 0
4 1 0
5 1 0
50 channel setup
1 330E-08 -7481545286
2 247E-06 -5606707399
3 1 0
4 1 0
5 1 0
60 channel setup
1 186E-05 -4731050136
2 951E-05 -4021609465
3 1 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Attenuation(dBkm)
30 channel system
1 562E-30 -2925058218
2 156E-25 -2480578547
3 901E-18 -1704537403
4 386E-09 -8413552232
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
42
Table3 Data for uncompensated Setups (Varying channel spacing)
5 0000568868 -3244988496
40 channel system
1 598E-15 -14223362
2 586E-14 -1323216612
3 103E-11 -1098820972
4 103E-07 -6988154773
5 0000690223 -3161010573
50 channel system
1 313E-08 -7504158834
2 531E-08 -7274840053
3 226E-07 -6645755145
4 798E-06 -5098023232
5 000151322 -2820097927
60 channel system
1 186E-05 -4731050136
2 951E-05 -4021609465
3 100E+00 0
4 1 0
5 1 0
FSO
MinBER Log(MinBER)
Length(Km)
01 THZ
1 111E-23 -2295322788
2 388E-11 -1041126679
3 000209342 -2679143631
4 1 0
5 1 0
02 THZ
1 303E-205 -2045185774
2 900E-22 -2104556355
3 000217247 -2663046212
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
43
4 1 0
5 1 0
03 THZ
1 621E-170 -1692068951
2 364E-18 -1743941554
3 000425754 -2370841263
4 1 0
5 1 0
005 THZ
1 193E-08 -7714667772
2 221E-04 -3655295382
3 000280352 -2552296341
4 1 0
5 1 0
002 THZ
1 571E-08 -7243166184
2 422E-07 -6374908869
3 807E-07 -6093092563
4 135E-06 -586963728
5 588E-06 -5230561375
Table4 Data for Compensated Setups(varying FSO length)
FSO MinBER Log(MinBER)
Length(Km)
Pre-Compensated
1 800E-57 -5609715546
2 309E-55 -5451015679
3 445E-49 -48351803
4 366E-31 -3043659961
5 408E-11 -1038893447
Post-Compensated
1 609E-63 -6221543406
2 513E-61 -6028961181
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
44
Table5 Data for Amplified Setups
3 399E-53 -5239903255
4 244E-32 -3161344575
5 417E-11 -1038032348
Symmetric
Compensated
1 565E-18 -1724782397
2 805E-18 -1709441403
3 553E-18 -1725762684
4 670E-18 -17174097
5 863E-18 -1706402594
FSO MinBER Log(MinBER)
Length(Km)
Using SOA
1 229E-08 -764016
2 481E-09 -831785
3 206E-09 -868613
4 197E-11 -107055
5 319E-10 -9496209
6 363E-07 -6440093
7 588E-08 -7230622
8 196E-09 -8707743
9 491E-10 -9308918
10 104E-08 -7982966
11 203E-07 -6692503
12 130E-05 -4886056
Using EDFA
1 112E-24 -2395078
2 239E-21 -2062160
3 108E-15 -1496657
4 490E-10 -9309803
5 134E-05 -4872895
6 452E-03 -2344861
7 100E+00 0
8 100E+00 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
45
Table 6 Data for Pre- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 200E-65 -6469940234
2 339E-64 -6346959025
3 638E-61 -6019508199
4 183E-51 -5073669066
5 332E-30 -2947908959
20Gbps
1 139E-73 -7285657297
2 598E-73 -7222354944
3 218E-68 -6766207774
4 620E-52 -5120772811
9 100E+00 0
10 100E+00 0
11 100E+00 0
12 100E+00 0
Using SOA+EDFA
1 147E-06 -583268
2 733E-09 -813489
3 368E-08 -743415
4 119E-08 -792445
5 177E-09 -875202
6 693E-11 -101592
7 901E-14 -130452
8 208E-17 -166819
9 361E-20 -194424
10 242E-21 -206161
11 953E-21 -200209
12 189E-17 -167235
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
46
5 484E-24 -2331520938
40 Gbps
1 134E-64 -6387202425
2 435E-64 -6336193226
3 151E-58 -5782225001
4 898E-39 -3804654331
5 600E-14 -132220674
50 Gbps
1 848E-04 -3071349177
2 904E-04 -3043935351
3 000104213 -2982078102
4 000154961 -280977759
5 000516721 -2286743888
Table 7 Data for Post- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 364E-74 -7343847407
2 880E-73 -7205558939
3 134E-68 -6787194016
4 941E-57 -560264653
5 793E-32 -3110098648
20Gbps
1 317E-89 -8849840266
2 247E-87 -866069568
3 174E-79 -787586478
4 140E-56 -5585356186
5 234E-24 -236308324
40 Gbps
1 119E-78 -7792501909
2 148E-77 -7683017573
3 903E-69 -6804417184
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
47
4 178E-42 -4174918005
5 319E-14 -1349648714
80 Gbps
1 781E-04 -3107083244
2 832E-04 -3079760808
3 0000965268 -3015352091
4 000145471 -2837223576
5 000504419 -2297208563
Table 8 Data for Symmetric- compensated Setups (Varying Data Rate)
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 662E-66 -6517911183
2 124E-65 -6490508537
3 463E-66 -6533485258
4 773E-66 -6511204305
5 330E-65 -6448116901
20Gbps
1 496E-90 -8930423035
2 334E-87 -8647594288
3 961E-88 -8701749494
4 409E-86 -8538811744
5 320E-83 -8249534839
40 Gbps
1 459E-40 -3933793476
2 541E-39 -3826665024
3 192E-38 -3771619013
4 928E-38 -3703251287
5 266E-36 -355752637
80 Gbps
1 274E-03 -2562663324
2 272E-03 -2564945979
3 000267567 -2572567451
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
48
Table 9 Data for Uncompensated Setups (Varying Data Rate)
4 000267321 -2572966923
5 000268876 -2570447961
Data MinBER Log(MinBER)
Rate(Gbps)
10 Gbps
1 456E-53 -5234077713
2 972E-34 -3301230291
3 243E-07 -6614602882
4 100E+00 0
5 100E+00 0
20Gbps
1 225E-53 -5264704994
2 156E-25 -2480668057
3 151E-04 -3819819626
4 100E+00 0
5 100E+00 0
40 Gbps
1 557E-39 -3825423916
2 369E-15 -1443342111
3 607E-03 -2216708292
4 100E+00 0
5 100E+00 0
80 Gbps
1 231E-09 -8635582221
2 423E-06 -5373860913
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
49
Table 10 Data for 30 channel uncompensated Setup (Varying Modulation Format)
65 Graphs and Discussions
The performance evaluating parameters extracted from Simulations were graphically
analyzed as follows
651 Varying FSO Length In Different Channels In Setups
It was observed from the graph shown in figure 651 that BER (bit error rate) value
increases with the increase in FSO length As the number of channels increase in the system
the performance of the system degrades The graph further depicts that 30 channel system
shows
FSO MinBER Log(MinBER)
Length(Km)
RZ Modulation
1 243E-46 -4561361876
2 512E-06 -5290504468
3 1 0
4 1 0
5 1 0
NRZ Modulation
1 176E-29 -2875412721
2 382E-11 -1041839846
3 1 0
4 1 0
5 1 0
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
50
best performance followed by 4050 and 60 channel systems Also the systems perform till
3 km of FSO length while as severe signal distortions were observed after 3 kms of FSO
length
Fig651 FSO Length Versus Log Min BER (Uncompensated)
652 Varying FSO Attenuation In Different Channels Setups
Fig652 FSO Attenuation Versus Log Min BER (Uncompensated)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
51
It was observed from the graph shown in Fig652 that the BER value goes on increasing
with the increase in attenuation of atmospheric channel for each system The graph further
depicts that the 30 channel system having Minimum BER value performs better followed
by 4050 and 60 channel setup It is also clear from the graph that system performance
severely degrades at an attenuation of greater than 10 dBKm
653 Varying Channel Spacing In Different Channel Setups
The graphs shown in below figures are plotted for different channel systems by varying
channel spacing A graph plotted for 30 channel system predicts that a system performs well
at 02 channel spacing followed by 03 However the decreased values degrade the
performance of the system that may due to the interference caused by closely spaced
channels A 40 channel system works better at 01 channel spacing followed by 02 amp 03
respectively A poor performance is observed at smaller values A same trend is followed by
50 amp 60 channel systems with a slight variation in BER values The graphs depict that a
nominal value of channel spacing should be chosen for transmission as the increased
channel spacing result in increased bandwidth utilization and a decreased value results in
interference between the channels
Fig653(a) FSO Length Versus Log Min BER (30 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
52
Fig653(b) FSO Length Versus Log Min BER (40 channel setup)
Fig653(c) FSO Length Versus Log Min BER (50 channel setup)
Fig653(d) FSO Length Versus Log Min BER (60 channel setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
53
654 Varying Compensation Techniques In 30 channel System
It was observed from the graph shown in figure 654 that the increase in FSO length results
in an increase in BER value for all the compensation schemes and uncompensated as well
Therefore the increase in FSO length for different compensation schemes results in the poor
performance of the system The graph also depicts that a 30 channel setup when
compensated by post compensation technique shows best performance followed by pre-
symmetric- and uncompensated schemes However a symmetric compensation technique
shows almost a linear response Also an uncompensated technique shows poor performance
than other relative techniques
Fig654 FSO Length Versus Log Min BER (30 Channel Setup)
655 Varying Data Rates In different 30 channel compensated models
The graphs for FSO length against Log Min BER was plotted for different data rates in all
compensated setups and uncompensated as well Two types of graphs were plotted a
particular system at different data rates and different systems at a particular data rate The
data rates are varied as 10 Gbps 20 Gbps 40 Gbps amp 80 Gbps For 10 Gbps data rate
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
54
Fig655(a) FSO Length Versus Log Min BER (at 10 Gbps)
Fig655(b) FSO Length Versus Log Min BER (at 20 Gbps)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
55
Fig655(c) FSO Length Versus Log Min BER (at 40 Gbps)
Fig655(d) FSO Length Versus Log Min BER (at 80 Gbps)
The observations from graphs are as
(A)From fig 655(a) It is observed that at 10 Gbps data rate post-compensated showing a
minimum value of BER amp performs better followed by pre-symmetric amp uncompensated
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
56
models A symmetric compensated setup shows almost a linear response Post- Pre- amp
symmetric setups show a sharp increase in BER value beyond 3 km of FSO length
(B)A graph plotted in fig655(b) shows that a symmetric model having a minimum value
of BER performs better and shows almost a linear response followed by post- pre- amp
uncompensated models at 20 Gbps data rate Pre- Post - amp uncompensated setups show a
sharp increase in BER value beyond 3 Km FSO length
(C)A graph in fig 655(c) indicates that at data rate of 40 Gbps Post-compensated model
performs best followed by pre- symmetric amp uncompensated systems Sharp increase in
BER is observed beyond 3 km of FSO length
(D)A 80 Gbps system is evaluated and the result is shown in fig 655(d)The graph
indicates that uncompensated model shows a minimum BER value and thus performs better
followed by post- pre- and symmetric setups
(E)A fig 655(e) shows that an uncompensated model performs best at 10 Gbps data rate
The increase in data rate results in performance degradation of the system At 80 Gbps the
system shows poor performance for greater than 3 km of FSO length
(F)A graph shown in fig 655(g) indicates that a pre-compensated model performs better at
20 Gbps for less than 4 km followed by 10 Gbps 40 Gbps amp 80 Gbps However beyond 4
km FSO length 10 Gbps data rate results in better performance of system
(G)A graph shown in fig 655(h) indicates that a post-compensated model performs better
at 20 Gbps followed by 40 Gbps 10 Gbps amp 80 Gbps data rates At 80 Gbps data rate the
system shows poor performance
(H)A symmetric compensated setup is evaluated at different data rates and the result is
shown in fig 655(i)The result shows that a system performs best at 20 Gbps data rate
with almost linear response followed by 10 Gbps 40 Gbps amp 80 Gbps data rates
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
57
Fig655(e) FSO Length Versus Log Min BER (for uncompensated setup)
Fig655(f) FSO Length Versus Log Min BER (for pre-compensated setup)
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
58
Fig755(g) FSO Length Versus Log Min BER (for post-compensated setup)
Fig655(h) FSO Length Versus Log Min BER (for symmetric-compensated setup)
66 Varying amplifiers In 30 channel System
Various graphs drawn for different channel Spacings are as under
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
59
FSO LENGTH(KM)
Fig66 FSO Length Versus Log Min BER(30 channel Setup)
A graph of Log of MinBER against variable FSO length as shown above was plotted for the
FSO setup incorporating various Amplification Techniques and the following inferences
were drawn from the graph
(a)The BER values show a general increase with increase in FSO length
(b)Out of all the propose amplification techniques the uncompensated setup shows the
highest BER values for particular FSO length
(c)The hybrid amplification technique proved to be best for longer FSO lengths while as for
shorter FSO lengths EDFA based amplification technique proved to be more efficient
(d)The response of SOA based amplification techniques was nearly linear for almost all the
FSO lengths
(e)It was also observed that the maximum supported FSO length was improved by
amplification techniques of SOA amp hybrid setup from being limited to a maximum of 3 km
in case of uncompensated to a maximum of 12 kms in case of proposed amplification
techniques
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
60
67 Varying Modulation Format In 30 channel System
Fig67 FSO Length Versus Log Min BER (Uncompensated 30 channel seup)
From figure 67 (f) the graph shows that the increase in FSO length results in increase in
BER value for different modulation formats hence resulting in poor performance It is also
clear from the graph that BER values for RZ modulation are lower than that of NRZ
modulation Therefore an optical source when set with RZ modulation shows better results
than NRZ modulation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
61
CONCLUSION
A number of techniques and methods have been proposed and implemented in the past years
to increase the number of users in the system and transmit the data to maximum possible
range with minimum losses In this thesis the features of DWDM technology Hybrid
amplifiers and FSO are merged in a single system to improve the performance of the
system The work also includes variation of various system parameters like number of
channels attenuation modulation format channel spacing and data rates It is concluded
that a nominal value of channel spacing should be selected for transmission as the increased
value of channel spacing results in increase in bandwidth utilization and the decreased
values result in interference between the channels Some compensation techniques are also
implemented in the system to obtain the better results While varying number of channels in
a system it is observed that 30 channel system show better results followed by 4050 and 60
channel setup and the FSO range supported by the systems is less than 3 km The change in
attenuation for different systems proved 30 channel system to perform best followed by
4050 and 60 channel setup however a serious signal distortion is observed for attenuation
value greater than 10 dBkm when the modulation format of optical source in 30 channel
system is varied from RZ to NRZ format the results for RZ modulation are observed to be
better than the later To compensate the losses in the system compensation techniques are
used and the post-compensation technique shows best performance followed by pre-
compensation symmetric-compensation and uncompensated as well It is observed that a
post-compensated setup performs better followed by pre- symmetric amp uncompensated
models The research work also includes incorporation of different amplifiers including
hybrid combination in the system to get the better results The use of SOA amp hybrid
combination Of EDFA amp SOA increases the range of FSO link beyond 4 Kms upto 12 Kms
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
62
FUTURE SCOPE
In this thesis 30 channel system is considered for carrying out the major part of research
The work can be extended by investigating the other channel systems also This thesis
includes the the use of compensation techniques to reduce the losses resulting from
dispersion In future work can be extended to limit the effect of geometrical and
geographical losses onto the performance of FSO networks Moreover modified devices
can be suggestedproposed that help in improving overall SNR of systemFSO networks as
of now are limited to shorter distances work can be extended to propose FSO networks for
longer distances as well The work also includes analysis of some amplifiers like SOA
EDFA and hybrid combination of SOA ampEDFA the other amplifiers and their hybrid
combinations like Raman-EDFA etc can also be explored in the system Further the
systems with combinations of more than two amplifiers can also be demonstrated The
effect of varying the other system parameters like channel spacing data rate input power
can be applied to the proposed system to improve the results
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
63
APPENDIX-I
Proposed workplan with Timeline for Dissertation-II
Week Week 1 week 2 Week 3 Week 4
Month
January
Design
different
channel setups
Worked on
FSO Length
Worked on
Attenuation
Worked on
Varying Channel
spacing
February
Compared
channel spacing
results
Worked on
compensation
schemes
Compared
different
compensation
schemes
Using different
amplifiers
March
Compared
amplifier
results
Varying
modulation
formats
Compared
modulation
results Varying data rates
April
Compared data
rate results Result Report writing Report writing
Compilation
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
64
REFERENCES
[1] Vishal Sharma Gurmindeep kaur ldquoHigh speed long reach OFDM ndashFSO to link
incorporating OSSB amp OTSB schemesrdquo optic 2013
[2] Sooraj parkash Anurag Sharma Harsukhpreet singh and Harjit pal singh ldquoperformance
investigation of 40 GBs DWDM over free space optical communication system using RZ
modulation formatrdquo Hindawi 2016
[3] Surabh Dubey Sachin Kumar Rajesh Mishra ldquo simulation and performance evaluation of
free space optic transmitter systemrdquo IEEE 2014
[4] httpimageslidesharecdncomfreespaceopticalcommunicationfinal-1504260341
[5] R J Hoss and E A Lacy ldquo Fiber optics 2nd edition New jersey 1993
[6] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[7] T okoshi and K kikuchi ldquocoherent optical fiber communication Boston 1989
[8] httpuploadwikimediaorgwikipediacommonsthumb|9|9b|TDM-operatingprinciple
[9] G P Agarwal ldquo Fiber optic communication systems Singapore 1993
[10] A Hasegwa ldquooptical soliton in fibersrdquo springer 1989
[11] GP Agrawal ldquoFiber Optic Communication Systemsrdquo John Wiley and Sons New York1997
[12] Biswanath Mukherjee ldquoOptical WDM Networksrdquo Springer New York 2006
[13] Simranjit Singh amp RS Kaler ldquo Novel Optical Flat-Gain Hybrid Amplifier for Dense
Wavelength Division Multiplexed Systemrdquo IEEE Photonics Technology Letters VOL 26
NO 2 January 15 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
65
[14 ]Xiaojie Guo amp Chester Shu ldquocross-Gain Modulation Suppression In a Raman-Assisted
Fiber Optical Parametric Amplifierrdquo Jounal Of Lightwave Technology2014
[15] Mahmoud Jazayerifar Stefan Warm Robert Elschner Dimitar Kroushkov Isaac
Sackey Christan Meuer Colija Schubert amp Klaus Peterman ldquoJournal of
lightwavetechonologyrdquo VOL31 NO9 May12013
[16] Hardeep Singh Sukhwinder Singh ldquo Performance Analysis of Hybrid optical
amplifiers in 12010 Gbps WDM optical network with channel spacing of 50 GHZrdquo
Advances in coupling amp information technology ndashCCII2014
[17] Xiaojie Guo ampChester shu ldquo Investigation of Raman-Assisted crosstalk Reduction in
Multi-Wavelength Fiber optical parametric Amplificationrdquo Journal of light wave
technology VOL33NO23 December 1 2015
[18]Simranjit Singh and RSKaler ldquo Flat Gain L ndashBand Raman EDFA Hybrid optical
Amplifier For Dense Wavelength Division Multiplexed systemrdquo IEEE Photonics
Technology Letters VOL25 NO3 February 1 2013
[19] Thomas Toroundas Magnus Karlsson and Peter A Andreksonldquo Theory of
experiments Journal of Light wave technology VOL23 Issue 12PP-4067 -2005
[20] MFC Stephens IOPhillips PRosa PHarpaamp NJ Doranldquo Improved WDM
Performance of a fibre optical parametric amplifier using Raman assisted pumpingrdquo optics
express VOL23 NO2 Jan 2015
[21] Contestable M Presi AD Errico VGuarino and M Mat Sumoto ldquo 128 terrabit (
32 40 G bit S) WDM transmission over a double pass free space optical linkrdquo
[22] Vishal Sharma Gurimandeep Kaur ldquoHigh speed high reach OFDM-FSO transmission
link incorporated OSSB amp OTBS schemardquo optics VOL124 2013
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
66
[23] Sooraj Parkash Anurag Sharma Manoj Kaur amp Harsukh Preet Singh ldquo Performance
enhancement of WDM- PON FFTH network by using decision feedback amp feed forward
equalizationrdquo International Journal of Signal processing image processing and pattern
recognition VOL8 NO 8 PP 99-106 2015
[24] G Nykolass PF Szajowski A Cashion HM Presby GE Tourgee and JJAuborn
ldquoA 40 Gbs DWDM free space optical transmission link over 44 kmrdquo Free space laser
communication technologies VOL39322000
[25] Jasvir Singh Pushpa Gilawat Balkrishna Shah ldquo Performance evaluation of 3240
Gbps (12Tbps) FSO link using RZamp NRZ line codesrdquo International Journal of computer
applications VOL 85 NO4 January 2014
[26] Amminder Kaur Sukhbir Singh RaJeev Thakurldquo Review paper free space opticsrdquo
IJARCSSE VOL 14Issue 5 Aug 2014
[27] Pooja Kumari Rajeev Thakurldquo Review Paper Hybrid amplifiers in FSO systemrdquo
IJCT VOL 3 Issue 2 2016
[28] S Guizani ACheriti M Razak Y Boushmani HHamamldquo A new optical post
compensation technique for chromatic dispersion application to fibre- fed wirelessrdquo
International conference on wireless networks communications and mobile computing
2005
[29] Rajani Raju Pal Vishal Sharma ldquo Comparison of pre- post- and symmetrical
Dispersion compensation schemes for 1015 Gbps using different modulation formats at
various optical power levels using standard and Dispersion compensated fibresrdquo
International Journal of computer applications VOL 50 NO 21 July 2012
[30] Alla Abbas Khadir BaydaaFDhahir Xiquam Fu ldquo Achieving optical fibre
communication Experiments by optisystemrdquo International Journal of computer science and
mobile computing VOL3 P42-53 2014
Analysis Of FSO Signal Transmission Using Dense Wavelength Division Multiplexing Method
67
[31] Mohammad Ali Khalighi Murat Uysal ldquo Survey on free space optical communication
A communication Theory of Perspectiverdquo IEEE communication Surveys and Tutorials
VOL 16NO 42014
[32] Ankita Shivhare Ankita Mowar ampSoni Chiglani ldquo Design and Analysis of BER of 200
Gbps free space optical communication system with varying Receiver aperturerdquo
International Journal of computer applications VOL 120NO3 June 2013
[33] Nishal Sharma Mini Lumba Gurimandeep Kaur ldquo Severe climate sway in coherent
CDMA-OSSB -FSO transmission systemrdquo Optik VOL 1252014
[34] Shao Hao Wang Lixin XU PKA Wai HwaYaw Tam ldquo Optimization of Raman
assisted fiber optical parametric amplifier gain rdquo Journal of Lightwave techonology
VOL29 NO8 April 15 2011
[35] R S Kaler Ajay K Sharma TS Kamal ldquo Comparison of pre-post- and symmetrical
dispersion compensation schemes for 10 Gbps NRZ links using standard and dispersion
compensated fibres optical communication rdquo VOL 209 Issue 1-3 August 2002 Page
NO 107-123
[36] Manpreet Kaur Himali Sarangal ldquoPerformance Comparison of pre-post- and
symmetrical- dispersion compensation using DCF on 40 Gbps WDM systemrdquo International
Journal of advanced research in electronics and communication Engineering VOL 4 Issue
3 March 2015
[37] Manpreet Kaur Himali Sarangal ldquo Analysis on Dispersion Compensation with DCF
SSRG-IJECErdquo VOL 2 Issue 2 February 2015
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